New York - It's getting harder and harder to take umbrage if someone calls you a Neanderthal.
According to two studies published on Wednesday, DNA from these pre-modern humans may play a role in the appearance of hair and skin as well as the risk of certain diseases.
Although Neanderthals became extinct 28 000 years ago in Europe, as much as one-fifth of their DNA has survived in human genomes due to interbreeding tens of thousands of years ago, one of the studies found, although any one individual has only about 2% of caveman DNA.
"The 2% of your Neanderthal DNA might be different than my 2% of Neanderthal DNA, and it's found at different places in the genome," said geneticist Joshua Akey, who led one of the studies. Put it all together in a study of hundreds of people, and "you can recover a substantial proportion of the Neanderthal genome".
Both studies confirmed earlier findings that the genomes of east Asians harbour more Neanderthal DNA than those of Europeans. This could be 21% more, according to an analysis by Akey and Benjamin Vernot, published online in the journal Science.
Still, "more" is a relative term.
According to the paper by geneticists at Harvard Medical School, published in Nature, about 1.4% of the genomes of Han Chinese in Beijing and south China, as well as Japanese in Tokyo come from Neanderthals, compared to 1.1% of the genomes of Europeans.
Anthropologists expressed caution about the findings.
Fewer than half a dozen Neanderthal fossils have yielded genetic material, said Erik Trinkaus of Washington University in St Louis, one of the world's leading experts on early humans. Using this small sample to infer how much Neanderthal DNA persists in today's genome is therefore questionable, he said.
As expected, since Neanderthals never existed in Africa, Africans and those who trace their ancestry to that continent have almost no Neanderthal DNA, the Harvard team found.
Human ancestors began migrating out of humanity's natal continent as early as one million years ago, paleoanthropologists infer from fossil evidence, and between 500 000 and 200 000 years ago evolved into the robust, large-browed Homo neanderthalensis in Western Europe.
Ever since scientists extracted DNA from the remains of Neanderthals, they have known that people today carry snippets of cavemen genes, in the amounts of 2% to 3%.
That clinched the case that Neanderthals and modern humans interbred, probably 40 000 to 80 000 years ago, soon after the latter arrived in Europe from Africa. The new studies add details about how much DNA and of what kind we inherited.
"The story of early human evolution is captivating in itself, yet it also has far-reaching implications for understanding the organisation of the modern human genome," Irene Eckstrand of the National Institutes of Health's National Institute of General Medical Sciences, which partially funded the research, said in a statement.
"Every piece of this story that we uncover tells us more about our ancestors' genetic contributions to modern human health and disease."